The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Friction pack clutches in automatic motor vehicle transmissions are generally pressure lubricated, that is, hydraulic (transmission) fluid under pressure is delivered to the friction clutch pack or its near vicinity to lubricate and cool the interleaved plates or discs of the clutch. Depending upon whether the clutch is engaged or disengaged, the hydraulic fluid flow will generally take one or another of two paths.
Moreover, depending upon the configuration of the automatic transmission, at least one of the paths will result in redirection of the hydraulic fluid flow often to at least one other, typically disengaged, friction clutch pack. This occurs because, generally speaking, the relaxed plates or discs of a disengaged clutch represent a fluid flow path. When this occurs, hydraulic fluid flow, while providing cooling, may significantly increase spin losses in the disengaged clutch due to the viscosity of the hydraulic fluid. This, of course, reduces the overall efficiency of the transmission and increases fuel consumption. It should be understood that if the clutch is engaged, fluid flow does not occur between the clutch plates and the problem addressed by this invention does not exist.
Thus, there is a need in the art to reduce spin losses of disengaged friction clutches in automatic transmissions caused by flow of hydraulic fluid from other components into and through such disengaged friction clutch plates or discs.